As is well-known, mining operations in the past for recovering various metals, e.g., lead, copper, have utilized high grade ore deposits where possible. Many of these deposits have been exhausted and mining of lower grade ores is increasing. The processing of these leaner ores consumes large amounts of time, labor, reagents, power and water with conventional processing.
In addition to the increased expense associated with the extraction of these metals from low grade ores, proposed processes for separation of certain of the sulfide ores are technically very difficult and involve elaborate and expensive equipment. In many cases the expense incurred by such separation would be greater than the commercial value of the metal, such that the mineral recovery, while theoretically possible, is economically unfeasible.
Copending patent application "Process for Beneficiating Sulfide Ores", Ser. No. 086,830 filed Oct. 22, 1979 teaches the treatment of sulfide ores with a metal containing compound under conditions such as to selectively enhance the magnetic susceptibility of the mineral values to the exclusion of the gangue, allowing for a separation of these values from the gangue. However, it appears as though the presence of various volatile compounds within the ore can have an adverse effect on the recovery of mineral values in a process which enhances the magnetic susceptibility of the mineral values. Pretreating the raw sulfide ore with heat in order to volatilize these various components, and thereafter selectively enhancing the magnetic susceptibility of the mineral values so that they may be separated from the gangue, substantially enhances the effectiveness of the separation of the mineral values from the gangue. Additionally, pretreatment with heat, optionally in the presence of various gaseous additives, enhances the basic process, apparently as a result of differing mechanisms.